erofs: address D-cache aliasing

commit 27917e8194f91dffd8b4825350c63cb68e98ce58 upstream.

Flush the D-cache before unlocking folios for compressed inodes, as
they are dirtied during decompression.

Avoid calling flush_dcache_folio() on every CPU write, since it's more
like playing whack-a-mole without real benefit.

It has no impact on x86 and arm64/risc-v: on x86, flush_dcache_folio()
is a no-op, and on arm64/risc-v, PG_dcache_clean (PG_arch_1) is clear
for new page cache folios.  However, certain ARM boards are affected,
as reported.

Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support")
Closes: https://lore.kernel.org/r/c1e51e16-6cc6-49d0-a63e-4e9ff6c4dd53@pengutronix.de
Closes: https://lore.kernel.org/r/38d43fae-1182-4155-9c5b-ffc7382d9917@siemens.com
Tested-by: Jan Kiszka <jan.kiszka@siemens.com>
Tested-by: Stefan Kerkmann <s.kerkmann@pengutronix.de>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250709034614.2780117-2-hsiangkao@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index aa59788a61e6e4530c264b2baaa637ad8ed7e1d4..86e088fd386ee5fde2f7403001c68266a9b6de1a 100644 (file)
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -342,14 +342,12 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
 
        if (outpages > inpages) {
                DBG_BUGON(!rq->out[outpages - 1]);
-               if (rq->out[outpages - 1] != rq->in[inpages - 1]) {
+               if (rq->out[outpages - 1] != rq->in[inpages - 1])
                        memcpy_to_page(rq->out[outpages - 1], 0, src +
                                        (interlaced_offset ? 0 : righthalf),
                                       lefthalf);
-               } else if (!interlaced_offset) {
+               else if (!interlaced_offset)
                        memmove(src, src + righthalf, lefthalf);
-                       flush_dcache_page(rq->in[inpages - 1]);
-               }
        }
        kunmap_local(src);
        return 0;

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 496e4c7c52a4e0123230c86f2999c9ba75a630c6..d852b43ac43e324e220e247bda22180727e55138 100644 (file)
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -122,9 +122,11 @@ static inline unsigned int z_erofs_pclusterpages(struct z_erofs_pcluster *pcl)
 
 /*
  * bit 30: I/O error occurred on this page
+ * bit 29: CPU has dirty data in D-cache (needs aliasing handling);
  * bit 0 - 29: remaining parts to complete this page
  */
-#define Z_EROFS_PAGE_EIO                       (1 << 30)
+#define Z_EROFS_ONLINEPAGE_EIO         30
+#define Z_EROFS_ONLINEPAGE_DIRTY       29
 
 static inline void z_erofs_onlinepage_init(struct page *page)
 {
@@ -143,7 +145,7 @@ static inline void z_erofs_onlinepage_split(struct page *page)
        atomic_inc((atomic_t *)&page->private);
 }
 
-static void z_erofs_onlinepage_endio(struct page *page, int err)
+static void z_erofs_onlinepage_end(struct page *page, int err, bool dirty)
 {
        int orig, v;
 
@@ -151,16 +153,20 @@ static void z_erofs_onlinepage_endio(struct page *page, int err)
 
        do {
                orig = atomic_read((atomic_t *)&page->private);
-               v = (orig - 1) | (err ? Z_EROFS_PAGE_EIO : 0);
+               DBG_BUGON(orig <= 0);
+               v = dirty << Z_EROFS_ONLINEPAGE_DIRTY;
+               v |= (orig - 1) | (!!err << Z_EROFS_ONLINEPAGE_EIO);
        } while (atomic_cmpxchg((atomic_t *)&page->private, orig, v) != orig);
 
-       if (!(v & ~Z_EROFS_PAGE_EIO)) {
-               set_page_private(page, 0);
-               ClearPagePrivate(page);
-               if (!(v & Z_EROFS_PAGE_EIO))
-                       SetPageUptodate(page);
-               unlock_page(page);
-       }
+       if (v & (BIT(Z_EROFS_ONLINEPAGE_DIRTY) - 1))
+               return;
+       set_page_private(page, 0);
+       ClearPagePrivate(page);
+       if (v & BIT(Z_EROFS_ONLINEPAGE_DIRTY))
+               flush_dcache_page(page);
+       if (!(v & BIT(Z_EROFS_ONLINEPAGE_EIO)))
+               SetPageUptodate(page);
+       unlock_page(page);
 }
 
 #define Z_EROFS_ONSTACK_PAGES          32
@@ -1060,7 +1066,7 @@ next_part:
                goto repeat;
 
 out:
-       z_erofs_onlinepage_endio(page, err);
+       z_erofs_onlinepage_end(page, err, false);
        return err;
 }
 
@@ -1163,7 +1169,7 @@ static void z_erofs_fill_other_copies(struct z_erofs_decompress_backend *be,
                        cur += len;
                }
                kunmap_local(dst);
-               z_erofs_onlinepage_endio(bvi->bvec.page, err);
+               z_erofs_onlinepage_end(bvi->bvec.page, err, true);
                list_del(p);
                kfree(bvi);
        }
@@ -1333,7 +1339,7 @@ out:
                /* recycle all individual short-lived pages */
                if (z_erofs_put_shortlivedpage(be->pagepool, page))
                        continue;
-               z_erofs_onlinepage_endio(page, err);
+               z_erofs_onlinepage_end(page, err, true);
        }
 
        if (be->decompressed_pages != be->onstack_pages)